установить позицию потока каталога (set the position of a directory stream)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
seekdir — set the position of a directory stream
Синопсис (Synopsis)
#include <dirent.h>
void seekdir(DIR *dirp, long loc);
Описание (Description)
The seekdir() function shall set the position of the next
readdir() operation on the directory stream specified by dirp to
the position specified by loc. The value of loc should have been
returned from an earlier call to telldir() using the same
directory stream. The new position reverts to the one associated
with the directory stream when telldir() was performed.
If the value of loc was not obtained from an earlier call to
telldir(), or if a call to rewinddir() occurred between the call
to telldir() and the call to seekdir(), the results of subsequent
calls to readdir() are unspecified.
Возвращаемое значение (Return value)
The seekdir() function shall not return a value.
Ошибки (Error)
No errors are defined.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
None.
Обоснование (Rationale)
The original standard developers perceived that there were
restrictions on the use of the seekdir() and telldir() functions
related to implementation details, and for that reason these
functions need not be supported on all POSIX-conforming systems.
They are required on implementations supporting the XSI option.
One of the perceived problems of implementation is that returning
to a given point in a directory is quite difficult to describe
formally, in spite of its intuitive appeal, when systems that use
B-trees, hashing functions, or other similar mechanisms to order
their directories are considered. The definition of seekdir() and
telldir() does not specify whether, when using these interfaces,
a given directory entry will be seen at all, or more than once.
On systems not supporting these functions, their capability can
sometimes be accomplished by saving a filename found by readdir()
and later using rewinddir() and a loop on readdir() to relocate
the position from which the filename was saved.
Будущие направления (Future directions)
None.
Смотри также (See also)
fdopendir(3p), readdir(3p), telldir(3p)
The Base Definitions volume of POSIX.1‐2017, dirent.h(0p),
sys_types.h(0p)
